Electrical switch and the like.



D. K. MORRIS & G. A. LISTER.

ELECTRICAL swmm AND THE LIKE.

APPLIUATION FILED SEPT. 22, 190B.

Patented June 29, 1909.

2 SHEETS-SHEET 1.

D. K. MORRIS & G. A. LISTER.

ELECTRICAL SWITCH AND THE LIKE.

APPLICATION FILED SEPT, 22, 1908.

2 SHEETS-SHEET 2.

Patented June 29, 1909.

UNITED s Ar s PATENT OFFICE.

DAVID KING MORRIS AND GEORGE ANSLOW LISTER, OF COVENTRY, ENGLAND.

ELECTRICAL SWITCH AND THE LIKE.

To all whom it may concern:

Be it known that we, DAVID KING Mortars and GEORGE ANsLow LISTER, subjects of Great Britain, residing at Carlton Works, Lockhurst Lane, Coventry, in the county of Warwick, England, have invented'new and useful Improvements Relating to Electrical Switches and the Like, of which the following is a specification.

This invention relates to electrical switches and like cut-out devices, and has for its ob ject to construct a simple and effective switch of the type in which automatic cut-out in the event of an overload or falling of the current below a predetermined value is effected by the operation of a thermal element.

The invention comprises the combination with a propriate contacts mounted on a movab e arm, of a strip or strips rigidly connected with such contacts and adapted to ex: pand ordeflect laterally under the heating effect of a current passing therethrough, together with a fixed retaining piece or catch with which the said strip or strips can normally engage, the arrangement being such that with an excess or diminution of current (according to the purpose for which the switch is designed), the strip of strips disengage from the retaining piece and permit the contact arm to be swung away from the fixed contacts by a suitably arranged spring.

Referring to the two accompanying sheets of explanatory drawings :Figure 1 is a side elevation and Fig. 2 a sectional plan showing in the closed condition a switch constructed in accordance with this invention. Fig. 3 is a side elevation of the switch in the open condition. Fig. 4 is a front elevation of the eX- pansible contact strips, and Fig. 5 a similar view showing a modified configuration of the said strips. Figs. 6, 7 and 8, are diagrammatic plans showing modified constructions of catches or retaining pieces.

The same reference letters in the different views indicate the same or similar parts.

In the construction as illustrated of an automatic cut-out-switch designed for operat- 'ing in the event of an overload, a pair of contacts a are secured to a su porting arm or lever l) and one at least 0 the contacts is insulated from the arm. The latter is carried on a bracket 0 which is attached to the ordinary base or back plate d of the switch. Preferably such contacts are made of a wedge like formation and the corresponding fixed contacts or brushes (1 on the switch back Specification 01 Letters Patent. Application filed September 22, 1908.

Patented June 29, 1909.

Serial No. 454,247.

plate are laminated and the contacting edges inclined to correspond with the contacts on the movable arm.

The operating handle e may be fixed to the contact arm, or it may be arranged to act independently of the contact arm, any suitable and ordinary provision being made in the latter case to effect the required connection between the arm and handle in the opening and closing movements. shown a lug or projection f is employed to effect the required connection between the two parts for the opening of the switch, the closing being effected as hereinafter dc scribed. In conjunction with the contact arm there is also provided a spring 9 for the purpose of breaking the circuit quickly.

Connection of the contact pieces a on the movable arm is effected by a pair of thermal elements comprising a pair of conducting elastic strips h secured rigidly at their errtremities to the contact pieces a, and thereby constrained to expand laterally under the heating efiect of a current passing through the same. Each strip has secured to it, at about the center, a steel catch engagement piece i. The latter is fixed in position preferably by rivets to avoid brazing and consequent softening of such piece. The

strips may be arranged parallel with each other as shown at Fig. i, or they may be initially adjusted to take up the configuration shown in Fig. 5.

On the back plate d of the switch there is ment with respect to the back plate may be effected by the nuts m whereby the catch is secured to such plate. When the switch is closed the engagement pieces i on the thermal elements spring into the grooves in the catch piece 7c and thereby retain the switch arm against the fixed contacts in opposition to the action of the spring g controlling the arm. The closing movement of the switch arm is arrested when the aforesaid engagement pieces lie opposite the catch grooves In the example by the abutment of a projection 1 from the handle against the catch which is grooved across the front face as shown. The contact arm is advanced into its closed position by the abutment of the said pro ection 72 against the pieces h of the contact connecting strips. The projection 01, is not essential, but convenient with the form of catch shown in Figs. 1 to 3. With the catch shown at Fig. 7, to be hereinafter referred to, the projection n may be dispensed w th.

In the event of an overload the strips are expanded laterally and the grip upon the catch is thereupon relaxed. he swltcharm consequently swings into the open position under the influence of its spring g. The amount of overload required to operate the cut-out may be varied if required y adjustin r the catch, or by the provision of a suitalile shunt mounted on the arm I). When the switch or circuit breaker is of the loose handle type, the thermal strips expand enough not only to clear the catch but also the abutment piece or projection 71. on the handle, so that the circuit is broken even if the handle is forcibly held up in the switch closing position. As an additional safeguard against the possibility of the switch contacts being forcibly held up during an overload the device shown at Fig. 6 is sometimes adopted. The front end of the catch is provided with a tapered recess 0 and the abutment iece or projection 72. from the handle is s otted'or bifurcated and formed with a tapered or conical extremity corresponding to the recess in the catch. hen the strips h approach the grooves in the catch under the action of the projection 'n the part 1) is pressed into the recess 0 and the shoulders of the projection abutting against the stri s are drawn together so as to diminish the breadth of contact with the pieces 1' of the stri s k. The parts are proportioned to make t e amount of contact between the shoulders of the abutment n and the pieces 2' of the strips it so small when the latter are in engagement with the catch that a relatively slight ex ansion of the strips will enable them to c ear the abutment. This device is more especially suitable for a switch of small size.

In Fig. 7 is shown a simplified catch produced entirely by turning operations from a cylindrical bar. Such catch consists of a stem formed with a circular head q behind an inclined shoulder of which the pieces '5 of the strips k can engage. When the switch is closed t e spring 9 )resses the pieces i against the said shoulder w ich is suitably inclined to assist the liberation of the stri s h on the expansion of the same under the eating action of the current. With this form of catch any suitable and ordinary type of loose handle may be fitted on the arm I).

In the application of the invention to switches intended to open the circuit in the event of the current falling below a certain amount, the contact connecting strips are designed to expand sufficiently when carrying a normal current to engage. with an appropriate catch piece. This arrangement 1s shown diagrammatically at Fig. 8,j being the stem, I" the catch, and i the engagement pieces of the strips it. As soon as the current falls below the normal the strips leave the catch and the movable arm swings away as hereinbefore described.

In some cases the engagement pieces on the ex ansible connecting strips may be dispensed with, and the frictional grip of the stri )s on a catch or retaining piece formed wit plain faces relied upon to hold the switch arm in its closed position.

Switches made as hereinbefore described are reliable in action and by their simplicity enable rigid and durable construction to be obtained. A further advantageous characteristic of our switches is the possession thereby of a time element or time lag, such that in the event of an overload the switches take an appreciable time to operate if the overload is small, but operate quickly when the overload is great. To insure relatively uick action of the switch in the event of o y small overload, and also if the switch is designed for small currents only, it is desirable to use for the thermal elements a harddrawn material of high specific resistance. 7

Having thus described our invention what we claim and desire to secure by Letters Patent is 1. In electrical switches and the like, the

combination comprising a movable arm, contacts mounted on said arm, a laterally deflectable conducting strip rigidly connected at its ends with said contacts, and a fixed retaining piece with which said strip can cooperate for holdin the arm in the closed position, substantia y as set forth.

2. In electrical switches and the like, the combination comdprising a movable arm, contacts, mounte on said arm, a pair of laterally deflectable conducting strips rigidly connected at its ends with said contacts, and a fixed retaining piece with which said stri scan cooperate for holding the arm in tfie closed position, substantially as set forth.

3. In electrical switches and the like, the combination comprising a movable arm, con tacts mounted on said arm, a laterally deflectable conducting strip rigidly connected at its ends with said contacts, an enga ing piece secured to said strip, and a fixe catch with which said piece on the strip can engage, substantially as set forth.

4. In electrical switches and the like, the combination comprising a movable arm, contacts mounted on the said arm, a pair of laterally deflectable conducting strips connected with said contacts, an engaging piece on each and an abutment piece on the said handle stri and a catch adapted for engagement by l both the said pieces on the strips, substantially as set forth. l

5. in electrical switches and the like, the combination comprisinga back 1plate, a mov-- able arm pivoted on said back p ate, contacts mounted on said arm, a air of laterally de- I ilectable conducting strlps connected with said contacts, an engaglng piece on g each strip, a catch secured to the back plate and 5 adapted for engagement by both the said en- E gaging pieces on the strips, a spring adapted to swing the arm away from the catch on the release of the same by. the engaging pieces, and a handle movable independently of the arm, substantially as set forth.

6. In electrical switches and the like, the combination comprising a back late, a movr able arm pivoted on said back p ate, contacts mounted-on said. arm, a pair of laterally deilectable conducting strips connected with said contacts, an engaging piece on each strip, a catch secured to the back plate and adapted for engagement by both the said engaging pieces on the strip, a spring adapted to swing the arm away from the catch on the release of the same by the engaging pieces, a handle movable independently of the arm,

adapted to press against the engaging pieces on the strips in the closin movement of the arm, substantiall as set orth.

7. In electrica switches and the like, the combination comprising a back late, a movable arm pivoted on said back p ate, contacts mounted on said arm, a pair of laterally deflectable conducting strips connected with said contacts, an engaging piece on each stri a catch adapted for engagement by boti the said engaging pieces on the strips and formed' at itsfront end with a tapered cavity, a spring adapted to swing the arm away from the catch on the release of the same by the engaging pieces, a handle movable independently of the arm, and a bifurcated abutment piece on the said handle adapted to press against the engaging pieces on the strips and also enter the tapered recess in the catch in the closing movement of the arm, substantially as set forth.

In testimony whereof we have signed our names to this specification in the presence of two subscribin r Witnesses.

DAV D KING MORRIS. GEORGE ANSLOVV LISTER. Witnesses:

CHARLES E. HULsE, E. PLAYER. 

